<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>boot css2</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="static/css/bootstrap.min.css">
</head>
<body>
<div class="container">
    <div class="row">
        <div class="col-lg-3 col-md-4 col-sm-6 col-xs-12 bg-info">a<br>a</div>
        <div class="col-lg-3 col-md-4 col-sm-6 col-xs-12 bg-success">a<br>a</div>
        <div class="col-lg-3 col-md-4 col-sm-6 col-xs-12 bg-danger">a<br>a</div>
        <div class="col-lg-3 col-md-4 col-sm-6 col-xs-12 bg-primary">a<br>a</div>
    </div>
    <hr>
    <div class="row">
        <div class="col-md-3 bg-danger">a<br>a</div>
        <div class="col-md-9 bg-warning" style="padding: 0;">
            <div class="col-md-6 bg-info">a<br>a</div>
            <div class="col-md-6 bg-success">a<br>a</div>
        </div>
    </div>


    <!--<div>
        <img class="img-rounded" src="static/imgs/html_css.jpeg">
    </div>
    <div>
        <img class="img-circle" src="static/imgs/html_css.jpeg">
    </div>
    <div>
        <img class="img-thumbnail" src="static/imgs/html_css.jpeg">
    </div>-->
</div>
</body>
</html>